Polyarylene sulfide resin

ABSTRACT

This invention relates to a novel polyarylene sulfide resin or a resin composition comprising said polyarylene sulfide resin moldable with reduced generation of flash. The polyarylene sulfide resin of this invention comprises 0.5-10% by weight of the constituent unit represented by the following general formula (1) and 80-99.5% by weight of the constituent unit represented by the following general formula (2): 
     
       
         —(Ar 1 —S—) n   (1) 
       
     
     
       
         —(Ar 2 —S—) m   (2) 
       
     
     wherein Ar 1  is the radical represented by general formula (3),                    
     Ar 2  is phenylene or alkyl-substituted phenylene radical, R 1 -R 7  are independently hydrogen atoms or lower alkyl radicals containing 1-3 carbon atoms and n and m are integers of 1 or more.

TECHNICAL FIELD OF THE INVENTION

This invention relates to novel polyarylene sulfide resins and, moreparticularly, to polyarylene sulfide resins which are moldable withreduced generation of flash.

BACKGROUND TECHNOLOGY

Polyphenylene sulfide resins (hereinafter referred to as PPS resins) arehigh-melting heat-resistant crystalline resins with excellent propertiesin respect to flow, resistance to organic solvents, electricalproperties and flame retardance. On account of these features, PPSresins are widely used in recent years as materials in the manufactureof parts of electrical and electronic instruments, automobiles andchemical instruments. However, the problem facing PPS resins is theirtendency to generate flash in injection molding of articles, forexample, connectors and the like. The following methods are disclosed tosolve this problem; to blend linear PPS resins with crosslinked PPSresins which melt turning gel-like, to blend PPS resins withpolyphenylene ether resins (JP 1997-157525 A), to blend low-viscosityPPS resins with high-viscosity PPS resins (JP 1995-278432 A) and toblend PPS resins with polybutylene naphthalate resins (JP 1998-292099A). However, any of these methods partly damages the excellentcharacteristics of PPS resins as the result of blending. Improvement ofmoldability by copolymerization of PPS resins with polymers containingspecified epoxy radicals is disclosed in JP 1990-182726 A, but partialdamage of PPS resins also occurred here.

An object of this invention is to provide novel polyarylene sulfideresins moldable with reduced generation of flash when molded bythemselves or as part of resin compositions.

DISCLOSURE OF THE INVENTION

This invention relates to a polyarylene sulfide resin comprising 0.5-10%by weight of the constituent unit represented by the following generalformula (1) and 80-99.5% by weight of the constituent unit representedby the following general formula (2):

—(Ar₁—S—)_(n)  (1)

—(Ar₂—S—)_(m)  (2)

wherein Ar₁ is the radical represented by general formula (3), Ar₂ isphenylene or alkyl-substituted phenylene radical, R₁-R₇ areindependently hydrogen atoms or lower alkyl groups containing 1-3 carbonatoms and n and m are integers of 1 or more.

Further, this invention relates to a polyarylene sulfide resincomposition comprising the aforementioned polyarylene sulfide resin.

Still further, this invention relates to a process for preparing apolyarylene sulfide resin by polymerizing polychloro aromatic compoundscomprising 0.5-10% by weight of a dichloroarylene represented by thefollowing general formula (4)

(wherein R₁-R₇ are as defined earlier) and 80-99.5% by weight of adichlorobenzene represented by the following general formula (5)(wherein Ar2 is phenylene or alkyl-substituted phenylene radical) in thepresence of an alkali metal sulfide.

Cl—Ar₂—Cl  (5)

This invention will be described in detail below. The polyarylenesulfide resin of this invention comprises 0.5-10% by weight, preferably1-8% by weight, of the constituent unit represented by theaforementioned general formula (1) and 80-99.5% by weight, preferably92-99% by weight, of the constituent unit represented by theaforementioned general formula (2).

In the first place, a process and raw materials generally used for thepreparation of the resin of this invention will be explained. Since thefollowing account is an example, it is needless to say that any resincomprising the aforementioned constituent units at the specified ratiois satisfactory as the resin of this invention.

A compound which generates the radical represented by general formula(3) as the constituent unit of the resin of this invention is at leastone of the compounds represented by the aforementioned general formula(4). A compound of this kind can be obtained from phthalic anhydride orits derivative and 2,5-dichloroaniline or its derivative. Here, theradicals R₁-R₇ are independently hydrogen atoms or lower alkyl groupscontaining 1-3 carbon atoms and preferably they are all hydrogen atoms.

A compound which generates the radical represented by the aforementionedgeneral formula (2) is represented by the aforementioned general formula(5). Here, Ar₂ is phenylene or alkyl-substituted phenylene radical,preferably phenylene radical. Concretely, it is one kind or more ofdichlorobenzenes selected from dichlorobenzene and alkyl-substituteddichlorobenzenes, and it is generally dichlorobenzene. There are ortho-,meta- and para-isomers for dichlorobenzenes and para-isomers arepreferable. More preferable is p-dichlorobenzene. In the case ofalkyl-substituted dichlorobenzenes, the alkyl radical preferablycontains 3 or less carbon atoms.

To be precise, a compound represented by general formula (4) and adichlorobenzene are so used that the proportions of the radicalrepresented by general formula (1) and the radical represented bygeneral formula (2) remain in the aforementioned range. However, sincethe proportions in the raw material roughly coincide with those in theresin, the raw materials are taken so that the compound represented bygeneral formula (4) accounts for 0.5-10% by weight, preferably 1-8% byweight, and the dichlorobenzene accounts for 80-99.5% by weight,preferably 92-99% by weight. If the proportion of the compoundrepresented by general formula (4) becomes less than 0.5% by weight,there would substantially be produced no effect for reducing generationof flash. On the other hand, if the proportion exceeds 10% by weight,the melt viscosity would become excessively high during molding therebydeteriorating moldability.

The polychloro aromatic compounds to be used as raw materials may be thecompounds represented by the aforementioned general formulas (4) and (5)alone or may additionally contain a small amount of other polychloroaromatic compounds. In the latter case, the amount of other polychlorocompounds is kept preferably at or below 10% by weight of the totalpolychloro aromatic compounds. The use of other polychloro aromaticcompounds introduces constituent units other than those represented bygeneral formulas (1) and (2) in proportion to the amounts of otherpolychloro aromatic compounds used.

The aforementioned other polychloro aromatic compounds includedichlorobiphenyl, dichlorodiphenyl ether, dichlorodiphenyl ketone anddichloronaphthalene. The compounds cited have isomers and preferable arethose compounds which have chlorine atoms in a symmetrical position, forexample, para isomers and 2,6- or 2,7-dichloronaphthalene. If necessary,trichlorobenzene and the like may be used.

The resin of this invention can be prepared according to a processpublicly known for the preparation of PPS resins. For example, a processfor preparing polymers of relatively low molecular weight disclosed inJP 70-3368 B and a process for preparing linear polymers of relativelyhigh molecular weight disclosed in JP 1977-12240 B are available.

In addition, a process for polymerization in the presence of sulfur, aprocess for polymerization in the presence of an alkali metal sulfideand a process for self-polymerization of a raw material such asp-chlorothiophenol are available. A variety of additives, catalysts andsolvents may be used in the aforementioned reactions.

A preferred process is the one which effects polymerization in thepresence of sulfur or an alkali metal sulfide. The amount of sulfursource, that is, sulfur or an alkali metal sulfide is 0.9-1.1 mole per 1mole of polychloro aromatic compound.

The process for polymerization in the presence of an alkali metalsulfide is based on the reaction to be effected in a polar solvent inthe presence of an alkali metal sulfide. A typical alkali metal sulfideis sodium sulfide, but a combination of hydrated sodium sulfide, sodiumsulfide or sodium hydrosulfide and sodium hydroxide or a combination ofhydrogen sulfide and sodium hydroxide may be used. Polar solvents usefulfor the reaction include aprotic organic polar solvents such as amides,lactams and urea compounds, N-methylpyrrolidone (NMP) being preferable.The reaction temperature is normally in the range of 220-370° C. and thereaction time is in the range of 1-20 hours.

The polyarylene sulfide resin of this invention must have a weightaverage molecular weight of 10,000 or more, preferably 20,000-200,000.The resin of this invention can be used singly as molding resin and canbe molded by injection and the like with reduced generation of flashcompared with the conventional PPS resins or those PPS resins which donot contain the constituent unit represented by general formula (1).Reduced generation of flash here means that the length of flash is lessthan that of the standard PPS resin (unmodified), preferably ½ or less,when the standard and test resins are molded under the same conditions(a dumbbell-shaped test specimen is injection-molded in accordance withASTM D638 and a reference should be made to the method described in theexamples for the detailed conditions).

The polyarylene sulfide resin of this invention may be used togetherwith other resins or with additives such as inorganic fillers to form aresin composition. Such other resins include other ordinary polyarylenesulfide resins and resins other than polyarylene sulfide resins such aspolyphenylene oxide resins (PPO), polyamides, polysulfones andpolybutylene terephthalate (PBT). The proportion of the polyarylenesulfide resin of this invention is preferably 10-90% by weight of thetotal resins in a given resin composition.

The polyarylene sulfide resin of this invention may be incorporated inan ordinary PPS resin to yield polyarylene sulfide resin composition Amoldable with reduced generation of flash. In this case, the content ofthe polyarylene sulfide resin of this invention is preferably 10-90% byweight. From the viewpoint of reduced generation of flash, the resincomposition is formulated so that the constituent unit represented byformula (1) in the total polyarylene sulfide resins containing PPS resinbecomes 0.1-10% by weight, preferably 0.5-10% by weight. That is, in thecase of the aforementioned formulation, supposing the proportion of theresin of this invention to be incorporated in PPS resin is A % by weightand the proportion of the constituent unit represented by formula (1) inthe resin of this invention is B % by weight, the value of A or B may bevaried so that A×B=10-1,000, preferably 50-1,000, and the value of B mayexceed the aforementioned range of 0.5-10.

Furthermore, in blending of ordinary PPS resin with one of those resinswhich are amenable to blending with ordinary PPS resin, it is possibleto substitute the polyarylene sulfide resin of this invention or theaforementioned polyarylene sulfide resin composition A for a whole orpart of ordinary PPS resin to yield a polyarylene sulfide resincomposition B moldable with reduced generation of flash. The resinsamenable to blending with ordinary PPS resin include publicly knownresins such as polycarbonates, PPO, polyamides, polysulfones, PBT, PETand polystyrene. In this case, the content of the polyarylene sulfideresin of this invention is preferably 10-90% by weight of the totalresins. From the viewpoint of reduced generation of flash, the amount ofthe polyarylene sulfide resin of this invention or the aforementionedpolyarylene sulfide resin composition A to be incorporated is preferablyso chosen that the proportion of the constituent unit represented byformula (1) in the total polyarylene sulfide resins is in the range of0.1-10% by weight, preferably 0.5-10% by weight.

Further, it is allowable to incorporate inorganic fillers in thepolyarylene sulfide resin of this invention or in the aforementionedpolyarylene sulfide resin composition A or polyarylene sulfide resincomposition B to yield polyarylene sulfide resin composition C.Inorganic fillers are not restricted and those which are fibrous,powdery, granular or scaly may be used. The fibrous fillers includeglass fibers, asbestos fibers, carbon fibers, silica fibers and aramidfibers. The powdery, granular or scaly fillers include silica, alumina,talc, mica, kaolin, clay, silica-alumina, calcium carbonate, glass,glass beads and carbon black.

Further, in addition to the aforementioned ingredients, it is allowableas needed to incorporate in the polyarylene sulfide resin of thisinvention, polyarylene sulfide resin composition A, polyarylene sulfideresin composition B or polyarylene sulfide resin composition C otherpublicly known additives such as antioxidants, UV absorbers, partingagents, heat stabilizers, lubricants and colorants.

Preferred Embodiments of the Invention

This invention will be described further below with reference to theaccompanying examples, but will not be limited to these examples.

Determination of the Molecular Weight of Resin

The molecular weight of resin was determined by the use of a gelpermeation chromatograph equipped with a multiangle light scatteringdetector and a UV/VIS detector available from Senshu Scientific Co.,Ltd.

Determination of Glass Transition Temperature (Tg)

The glass transition temperature was determined by the use of DSC 7available from Perkin-Elmer Corporation.

Measurement of Flashing Characteristics

A dumbbell-shaped test specimen was injection-molded in accordance withASTM D638 and the length of flash was measured. The injection pressurewhich greatly influences the generation of flash was controlled at alevel which does not cause short shots.

EXAMPLE 1

Comparative

In an autoclave were placed 1.0 mole of sodium sulfide (purity, 61.5%)and 280 g of N-methyl-2-pyrrolidone (NMP) and the mixture was heated to202° C. over a period of approximately 2 hours to distill 22.7 g ofwater while blowing nitrogen gas into the autoclave. The reactionmixture was cooled to 175° C., 0.10 mole of sodium acetate trihydrate,50 g of NMP and 1.02 mole 1,4-dichlorobenzene (DCB) were added and theresultant mixture was allowed to react at 245° C. for 3 hours in anatmosphere of pressurized nitrogen gas (0.14 MPa). The reactor wascooled and the product was taken out and washed with hot water. A PPSresin with a Tg of 84° C. and a Tm of 285° C. was obtained in 94% yield.

EXAMPLES 2-4

Polyarylene sulfide resins (modified PPS resins) were prepared as inExample 1 while substituting N-(2,5-dichlorophenyl)phthalimide (DCPPI)for a portion of the DCB. The weight ratio of DCB to DCPPI was 99:1 inExample 2, 95:5 in Example 3 and 90:10 in Example 4.

EXAMPLE 5

Comparative

A modified PPS resin was prepared as in Example 1 except using a mixtureof DCB and DCPPI at a weight ratio of 80:20.

The molecular weight, Tg, and flashing characteristics were determinedfor the product in each example and the results are shown in Table 1.

TABLE 1 Molecular weight Length of flash (Mw) (μm) Tg (° C.) Example 13.7 × 10⁴ 520  85 Example 2 3.5 × 10⁴ 80 93 Example 3 3.7 × 10⁴ 30 112Example 4 3.2 × 10⁴ 10 138 Example 5 3.4 × 10⁴ Unmoldable 168

EXAMPLE 6

A polymer blend of the polyarylene sulfide resin prepared in Example 3and commercial PBT resin (Toraycon 1401 X06 available from TorayIndustries, Inc.) at a weight ratio of 70:30 was pelletized andinjection-molded as in the aforementioned examples and the flashingcharacteristics were evaluated. The length of flash was 20 μm.

EXAMPLE 7

A polymer blend of the polyarylene sulfide resin prepared in Example 3and commercial PPO resin (Xyron 220 V/Z available from Asahi KaseiCorporation) at a weight ratio of 70:30 was pelletized andinjection-molded as in the aforementioned examples and the flashingcharacteristics were evaluated. The length of flash was 40 μm.

INDUSTRIAL APPLICABILITY

The novel polyarylene sulfide resin of this invention and a resincomposition comprising said polyarylene sulfide resin can be molded withmarkedly reduced generation of flash and are useful for molding avariety of articles, particularly connectors of electronic parts.

What is claimed is:
 1. A polyarylene sulfide resin comprising 0.5-10% byweight of the constituent unit represented by the following generalformula (1) and 80-99.5% by weight of the constituent unit representedby the following general formula (2): —(Ar₁—S—)_(n)  (1)—(Ar₂—S—)_(m)  (2) wherein Ar₁ is the radical represented by generalformula (3),

Ar₂ is phenylene or alkyl-substituted phenylene radical, R₁-R₇ areindependently hydrogen atoms or lower alkyl radicals containing 1-3carbon atoms and n and m are integers of 1 or more.
 2. A polyarylenesulfide resin as described in claim 1 wherein R₁-R₇ are all hydrogen. 3.A process for preparing a polyarylene sulfide resin which comprisespolymerizing polychloro aromatic compounds comprising 0.5-10% by weightof a arylenedichloride represented by the following general formula (4)and 80-99.5% by weight of a dichlorobenzene represented by the followinggeneral formula (5) in the presence of, an alkali metal sulfide,

 Cl—Ar₂—Cl  (5) wherein R₁-R₇ are independently hydrogen atoms or loweralkyl radicals containing 1-3 carbon atoms and Ar₂ is phenylene oralkyl-substituted phenylene radical.
 4. A polyarylene sulfide resincomposition which comprises the polyarylene sulfide resin described inclaim 1 in an amount corresponding to 10-90% by weight of the totalresins.